This invention relates to flexible couplings for joining two rotatable shafts or other rotating parts which may have their rotation axes endwise or axially misaligned and wherein torque is transmitted predominantly in one direction of rotation, and deals more particularly with such a coupling which can accommodate a substantial amount of angular and endwise misalignment while transmitting high amounts of power within a relatively small space envelope.
This invention further relates to improvements in the type of coupling shown generally by U.S. Pat. No. 3,481,158 and No. 3,592,021 and which improvements are particularly useful in cases where the coupling is used to transmit torque in only one direction of rotation or where the coupling is used to transmit a significantly higher amount of torque in one direction of rotation than in the other direction.
Flexible couplings are commonly used for joining two rotatable shafts or parts in a rotary power transmitting system. Of the two shafts or parts, one is a driving member and the other a driven member. The type of coupling to which this invention relates is one having a flex member with four elongated elements joined together in a rectangular arrangement and rigidly fixed at two opposite corners of the arrangement to the driving member while the remaining corners are rigidly fixed to the driven member. Shaft misalignment, both angular and endwise, is accommodated by bending of the elements of the flex member. Desirable features associated with this type of coupling include the ability to operate without lubrication thereby avoiding the environmental constraints imposed by lubricants, freedom from backlash and induced variations in rotational speed, and the ability to flex through substantial misalignment while providing a relatively rigid load path for transmitted torque. Flexible couplings of this type may be of relatively simple design while being capable of meeting the drive torque and flexing requirements for many shaft joinder applications.
During use of a coupling of the type in question, the rectangular flex member has two opposite flex elements which are in compression while its other two flex elements are in tension. As transmitted driving torque is increased the compressive flex elements tend to bow due to increased column loading. This bowing of the compressive elements also causes related distortion of the tension elements and thereby produces increased stress in all four elements which diminishes the capacity of the elements to withstand misalignment. As a result, either torque or misalignment which the coupling can handle is reduced. Bowing of the compressive elements and the attendant distortion of the tension elements also leads to vibratory forces which interfere with smooth rotation which is essential for high speed operation. An increase in material stiffness or general additional thickness of the flex member can reduce the compressive element bowing, but such measures are counter-productive to maintaining the flexing capacity of the coupling.
Therefore, an object of this invention is to provide improvements to flexible couplings of the type in question whereby the performance of the coupling with regard to torque, speed, service life and size is made better without seriously impairing the flexing capability of its flex member or members. Or alternatively, another object of this invention is the provision of a flexible coupling with the capacity to perform under conditions of power transmission and misalignment which exceed the conditions capable of being handled by present couplings.
It is another object of this invention to provide a flexible coupling of such structural efficiency that the cost of a coupling for a particular application may be reduced.